SPI_cursor_open

Name

Synopsis

Description

SPI_cursor_open sets up a cursor
(internally, a portal) that will execute a statement prepared by
SPI_prepare. The parameters have
the same meanings as the corresponding parameters to SPI_execute_plan.

Using a cursor instead of executing the statement directly has
two benefits. First, the result rows can be retrieved a few at a
time, avoiding memory overrun for queries that return many rows.
Second, a portal can outlive the current procedure (it can, in
fact, live to the end of the current transaction). Returning the
portal name to the procedure's caller provides a way of returning
a row set as result.

The passed-in parameter data will be copied into the cursor's
portal, so it can be freed while the cursor still exists.

Arguments

const char * name

name for portal, or NULL to let
the system select a name

SPIPlanPtr plan

prepared statement (returned by SPI_prepare)

Datum * values

An array of actual parameter values. Must have same
length as the statement's number of arguments.

const char * nulls

An array describing which parameters are null. Must have
same length as the statement's number of arguments.

If nulls is NULL then SPI_cursor_open assumes that no
parameters are null. Otherwise, each entry of the
nulls array should be ' ' if the corresponding parameter
value is non-null, or 'n' if the
corresponding parameter value is null. (In the latter case,
the actual value in the corresponding values entry doesn't matter.) Note that
nulls is not a text string, just
an array: it does not need a '\0'
terminator.

bool read_only

true for read-only
execution

Return Value

Pointer to portal containing the cursor. Note there is no
error return convention; any error will be reported via
elog.